1. Field of the Invention
This invention relates generally to electrochemical cells and, more particularly, to gas depolarized electro-chemical cells usable as hearing aid batteries and the like which are commonly referred to as button cells because of their button-like appearance. The gas depolarized cells of the present invention have an increased capacity for the physical size of the cell as well as an improved electrolyte seal.
A further aspect of the invention is the process of assembling the cell through a sequence of steps including a sizing operation which produces a sealed cell having a minimum number of components.
2. Description of the Prior Art
The concept of gas depolarized galvanic cells is old in the art as evidenced by the numerous issued patents. The most pertinent patents are the metal air battery patents which contain a hydrophobic membrane on the outside of the air electrode. A new application for this type of metal air cell is in the small battery field. The art is replete with conventional small cells, however, to date, there have been few applications of metal air cells to the button cell field. An example of a zinc air button cell is shown in the Aker et al. U.S. Pat. No. 3,746,580. Aker shows a gas depolarized galvanic button cell which uses an air cathode and a zonc anode.
The present invention is an improvement over this newer type of zinc air button cell in which the prior art problem of sealing has been substantially eliminated. That is, with the metal-air button type such as shown in the Aker et al. patent, there are sealing problems. For example, Aker must injection mold a strip of plastic on the outer edge of his electrode assembly to obtain a seal. This has the disadvantage of decreasing the usable volume of the cell as well as increasing both the cost and the difficulty in assembling the cell. The present invention overcomes this problem by utilization of a single insulator which simultaneously seals the cell and insulates the positive terminal of the cell from the negative terminal of the cell.
A further aspect of the present invention is that assembly of the cell has been greatly simplified by the use of components which serve dual functions and a sizing process that simultaneously seals and forms the components of the cell into an integral assembled and operative cell.
A still further aspect of the present invention is that the cell has greater energy capacity than prior art zinc button cells of the same physical size because there is virtually no duplication of components.